A vacuum fluorescent display is known as a technique related to a vacuum tube, and, for example, structures shown in Japanese Utility Model Publication No. 49-5240 (hereinafter referred to as “Patent Literature 1”) and Japanese Patent Application Laid Open No. 2007-42480 (hereinafter referred to as “Patent Literature 2”) are known. In Patent Literature 1, a linearly tensioned filament which emits thermoelectrons at a predetermined temperature or higher is referred to as “a heater H”. An anode arranged parallel to the filament (“a positive pole 4” in Patent Literature 1), and a grid arranged between the filament and the anode such that the grid faces the anode are provided (see FIGS. 1 and 2 of Patent Literature 1). A basic structure in Patent Literature 2 is the same as that of Patent Literature 1. As a control method for the vacuum fluorescent display shown in Patent Literatures 1 and 2, a driving system shown in “Vacuum Fluorescent Display (VFD) General Application Notes—Driving Method—Driving system” by NORITAKE ITRON CORP, searched on the Internet (<https://www.noritake-itron.jp/cs/appnote/apf100_vfd/apf201_houshiki.html>) on Dec. 19, 2014 (hereinafter referred to as Reference Document 1) is known.